The Design Of Current-feedback Operational Amplifer And Its Application

The developing history, present situation and trends of Current-feedback Operational Amplifier (CFOA)was summarized in this paper. The dominance and properties of the CMOS integrated CFOA were also described.The influencing factor of subthreshold MOSFET based on CMOS process were analyzed ,and pointed out that the MOSFET based on CMOS process was easier to be integrated in CMOS circuit than BJT transistors. Detailedly narrate the structure, theory of CFOA,and its abstract virtue against Voltage-feedback Operational Amplifier(VFOA),namely the frequent-independent bandgap and infinite Slew Rate.Analyzed the second-order effects.Design CMOS sub-circuits and thus the whole structure.Through analysis of lots of literature related to CFOA,the two buffers are the key cell in the CFOA structure.In this paper,we proposed a brand-new buffer that eliminates the voltage gap between positive and negative input of the amplifier in static condition;besides,we adopted rail-to-rail input and push-pull output structure,both of them were perfect choice of low power and low voltage enviroment;the active current mirror which decrease the operating voltage and area of the whole circuit was also used in the structure.Compared with CFOA that proposed in previous literature,this circuit possess higher SNR and precision,lower power dissipation.We simulated the CFOA circuit with simulation tool of Hspice, applyed 0.6μmCMOS process parameters(low Vth): its negative and positive supply were -1.5V and +1.5V respectively, Cc=5pf; Rc=50kOhm; Cout=1pf. Its power consumption was 2.262mW; and its input resistor was 4.5k Ohm, phase degree was 53.5o , the disparity between the two inputs was 3 mV, the bandgap was 5MhZ, open-loop gain was 100dB, and its CMRR and PSRR+ are 27dB and 11dB respectively.We designed an Analog-to-Digital Converter(for CMOS Image Sensor)based on CFOA,observed from simulation the ADC based on CFOA possessed a higher speed,broader bandgap against its counterparts based on VFOA.It also showed that this circuit adopted to low voltage, low power, high speed,high frequency circuits.Based on CFOA,we proposed operational circuits,such as multiplier and dividor;integrator;filter; oscillator.